What is the best way for element creation on the fly and being able to move it around?
Let's say I want to create rectangle, circle and polygon then I want to select the objects and move it around

And how is the performance of those three while in use for showing a web page?
Let's say I want to create three visually identical web page and have header, footer, widget and text content in them. The first one is created using full canvas, the second is created using svg, and the third is created using plain div html and css.

4 Answers
4

The short answer:

SVG would be easier for you, since selection and moving it around is already built in. SVG objects are DOM objects, so they have "click" handlers, etc.

DIVs are okay but clunky and have awful performance loading at large numbers.

Canvas has the best performance hands-down, but you have to implement all concepts of managed state (object selection, etc) yourself, or use a library.

The long answer:

HTML5 Canvas is simply a drawing surface for a bit-map. You set up to draw (Say with a color and line thickness), draw that thing, and then the Canvas has no knowledge of that thing: It doesn't know where it is or what it is that you've just drawn, it's just pixels. If you want to draw rectangles and have them move around or be selectable then you have to code all of that from scratch, including the code to remember that you drew them.

SVG on the other hand must maintain references to each object that it renders. Every SVG/VML element you create is a real element in the DOM. By default this allows you to keep much better track of the elements you create and makes dealing with things like mouse events easier by default, but it slows down significantly when there are a large number of objects

Those SVG DOM references mean that some of the footwork of dealing with the things you draw is done for you. And SVG is faster when rendering really large objects, but slower when rendering many objects.

A game would probably be faster in Canvas. A huge map program would probably be faster in SVG. If you do want to use Canvas, I have some tutorials on getting movable objects up and running here.

Canvas would be better for faster things and heavy bitmap manipulation (like animation), but will take more code if you want lots of interactivity.

I've run a bunch of numbers on HTML DIV-made drawing versus Canvas-made drawing. I could make a huge post about the benefits of each, but I will give some of the relevant results of my tests to consider for your specific application:

I made Canvas and HTML DIV test pages, both had movable "nodes." Canvas nodes were objects I created and kept track of in Javascript. HTML nodes were movable Divs.

I added 100,000 nodes to each of my two tests. They performed quite differently:

The HTML test tab took forever to load (timed at slightly under 5 minutes, chrome asked to kill the page the first time). Chrome's task manager says that tab is taking up 168MB. It takes up 12-13% CPU time when I am looking at it, 0% when I am not looking.

The Canvas tab loaded in one second and takes up 30MB. It also takes up 13% of CPU time all of the time, regardless of whether or not one is looking at it. (2013 edit: They've mostly fixed that)

Dragging on the HTML page is smoother, which is expected by the design, since the current setup is to redraw EVERYTHING every 30 milliseconds in the Canvas test. There are plenty of optimizations to be had for Canvas for this. (canvas invalidation being the easiest, also clipping regions, selective redrawing, etc.. just depends on how much you feel like implementing)

There is no doubt you could get Canvas to be faster at object manipulation as the divs in that simple test, and of course far faster in the load time. Drawing/loading is faster in Canvas and has far more room for optimizations, too (ie, excluding things that are off-screen is very easy).

Conclusion:

SVG is probably better for applications and apps with few items (less than 1000? Depends really)

Canvas is better for thousands of objects and careful manipulation, but a lot more code (or a library) is needed to get it off the ground.

HTML Divs are clunky and do not scale, making a circle is only possible with rounded corners, making complex shapes is possible but involves hundreds of tiny tiny pixel-wide divs. Madness ensues.

The Cake library is another example of doing moveable objects and animations with objects on a canvas
–
SiggyFMay 4 '11 at 20:59

Wrong :P div's can scale if the browser is using hw accelerated CSS engine, css art is different and besides Canvas and SVG are the proper choice here , CSS art / div art is just when u dont need to overkill just a small overlay :P
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darkyen00Dec 6 '12 at 18:40

Concerning DIVs, if you want to make circles/special shapes and is not going to change its image/sprite due course, you can just create a PNG and use it as background-image... Though you can do similar things in SVG/Canvas
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luiges90Jul 7 '13 at 5:21

What if you are creating an interactive map game? :p
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AnthonyNov 20 '13 at 22:30

I have compared some visualization in Protovis (SVG) to Processingjs (Canvas) which display > 2000 points and processingjs is much faster than protovis.

Handling events with SVG is of course much easer because you can attach them to the objects. In Canvas you have to do it manually (check mouse position, etc) but for simple interaction it shouldn't be hard.

There is also the dojo.gfx library of the dojo toolkit. It provides an abstraction layer and you can specify the renderer (SVG, Canvas, Silverlight). That might be also an viable choice although I don't know how much overhead the additional abstraction layer adds but it makes it easy to code interactions and animations and is renderer-agnostic.

To add to this, I've been doing a diagram application, and initially started out with canvas. The diagram consists of many nodes, and they can get quite big. The user can drag elements in the diagram around.

What I found was that on my Mac, for very large images, SVG is superior. I have a MacBook Pro 2013 13" Retina, and it runs the fiddle below quite well. The image is 6000x6000 pixels, and has 1000 objects. A similar construction in canvas was impossible to animate for me when the user was dragging objects around in the diagram.

On modern displays you also have to account for different resolutions, and here SVG gives you all of this for free.

We settled on SVG too, after trying desperately to get Canvas to work for us. We have a very large diagram and SVG was by far the most efficient, plus the auto-scaling on retina screens is a massive bonus.
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FijjitJan 30 at 20:13

For your purposes, I recommend using SVG, since you get DOM events, like mouse handling, including drag and drop, included, you don't have to implement your own redraw, and you don't have to keep track of the state of your objects. Use Canvas when you have to do bitmap image manipulation and use a regular div when you want to manipulate stuff created in HTML. As to performance, you'll find that modern browsers are now accelerating all three, but that canvas has received the most attention so far. On the other hand, how well you write your javascript is critical to getting the most performance with canvas, so I'd still recommend using SVG.